Hello,
On Mon, 18 May 2020 13:25:50 +1200
Greg Ewing <greg.ew...@canterbury.ac.nz> wrote:
> On 18/05/20 1:59 am, Paul Sokolovsky wrote:
> > But even
> > {(int): str} is a better type annotation for a function than
> > Callable[[int], str].
>
> I don't agree -- it looks more like some kind of dict type, and
> would be better reserved for that purpose.
Well, I don't say "ideal", I say "better". The point is that the world
learned long ago that any type of information can be represented with
just recursive parens: (foo (bar 1 (2) 3)), but some variety in
punctuation helps mere humans among us.
>
> > And if we e.g. talk about making "->" a special operator which would
> > allow it to appear in other contexts
>
> Or maybe we could leverage the new walrus operator and write
>
> str := (int)
With the idea that someone may confuse ":=" for "<-", so we can swap
result and argument types comparing to their natural/intuitive order?
Well, I guess that's not what I'm talking about. But we indeed can treat
":=" as a function operator in annotations, and write:
(int) := str
Actually, we don't have to use funky novelties, and mere "-" looks
better as a lookalike for "->" than ":=". The following works as
expected:
=========
from __future__ import annotations
def foo(f: (str, int) - int = map, seq: list = None):
pass
print(foo.__annotations__)
import ast
print(ast.dump(ast.parse(foo.__annotations__["f"]).body[0]))
=========
I'd still consider it a better idea to just make "->" an operator on
the AST level. Can stop there, because realistically (or sanely)
PEP-0563 annotations would be parsed via an AST (example above).
But if there's desire to assign some semantics to it, it can be that of
making a tuple, with precedence just above "," operator, so
"foo -> bar, 1 -> 2" would evaluate to ((foo, bar), (1, 2)).
Worst-case, can add a __rarrow__ dunder.
>
> --
> Greg
--
Best regards,
Paul mailto:pmis...@gmail.com
_______________________________________________
Python-ideas mailing list -- python-ideas@python.org
To unsubscribe send an email to python-ideas-le...@python.org
https://mail.python.org/mailman3/lists/python-ideas.python.org/
Message archived at
https://mail.python.org/archives/list/python-ideas@python.org/message/56BAIT46CLGQWYEOL7VU54VENG72QCNO/
Code of Conduct: http://python.org/psf/codeofconduct/
